The present invention relates to a range finder device used in, for example, a camera or the like.
Range finder devices can be classified into two types. In the active mode type, range finding light is projected onto an object and range finding is performed using reflection signal light. The passive mode type uses an image signal of the object. However, because the active mode type uses reflection signal light, it has a drawback in that it is disadvantaged when used on objects with low reflectance or which are at a considerable distance. The passive mode has a drawback in that it is unable to perform accurate range finding in dark scenes in which a picture signal is difficult to obtain or on flat objects having little variation in density.
In Jpn. Pat. Appln. KOKAI Publication Nos. 55-35399, 7-167646, and the like, there is disclosed a method in which range finding is performed using the two above-described modes in combination according to the environment surrounding the object.
By switching between the active mode and passive mode according to the environment surrounding the object, in this way, examples of cameras which can focus correctly for any scene have hitherto both been proposed and manufactured.
However, the above described technology amounts to no more than simply providing both modes side by side and uses a simple structure in which one of these two modes is chosen according to the object. Accordingly, in this type of structure, the space required for the two devices to be mounted together is wasted. Moreover, the wasteful provision of sensors and circuits is a factor in causing the costs to be increased. Further, time is often wasted as both range finding results must be compared in order to decide which mode to employ.
In particular, when the above described range finding modes are used in a camera, after the release operation is performed, if time is required to choose one of the two modes, then the camera ends up acting as a long release time lag camera which is unable to track the movement of the object. For example, even if the expression of a model was excellent at the moment the release button was operated, the expression may have changed during the time taken for the range finding. Accordingly, although the photographer had intended to record a fleeting moment, all that remains in the photograph is often an empty reminder of what the happy memory may have been. Accurate range finding is important, but it is also important to consider these types of photo opportunities in a camera, which is essentially a device for enabling the user to capture the instant that he or she intended to photograph.
Accordingly, an object of the present invention is to provide a range finder device which does away with difficulty to photograph objects, which is effective both cost-wise and space-wise and which has a shortened time lag.
In order to achieve the above objects, the first aspect of the present invention is a range finder device comprising: a light projecting section for projecting range finding light onto an object; a light receiving section for monitoring image patterns of the object; an integrating circuit for integrating an output signal from the light receiving section; a steady light component removing section for preventing an output signal accompanying steady light irradiated steadily onto the light receiving section from being fed to the integrating circuit; and a control section for setting, during range finding, a first mode in which the steady light component removing section is operated or a second mode in which the steady light component removing section is not operated, based on an output signal from the light receiving section.
Further, the second aspect of the present invention is a range finder device comprising: a light projecting section for projecting range finding light onto an object; a light receiving section onto which reflection signal light from the object is irradiated and which monitors image patterns of the object based on the reflection signal light; an integrating circuit for integrating an output signal from the light receiving section; a steady light component removing section for preventing an output signal accompanying steady light irradiated steadily onto the light receiving section from being fed to the integrating circuit; a first determining section for determining a spot configuration of the reflection light signal; a second determining section for determining a contrast of an image pattern of the object; and a control section for setting a first mode in which the steady light component removing section is operated or a second mode in which the steady light component removing section is not operated, based on the determination results of at least one of the determination by the first determining section and the determination by the second determining section.
Further, the third aspect of the present invention is a range finder device comprising: a light projecting section for projecting range finding light onto an object; a light receiving section for monitoring image patterns of the object; an integrating circuit for integrating an output signal from the light receiving section; a first steady light component removing section for preventing an output signal accompanying steady light irradiated steadily onto the light receiving section from being fed to the integrating circuit; and a second steady light component removing section for further removing steady light components from an output signal from the first steady light component removing section.
Further, the fourth aspect of the present invention is a range finder device comprising: a light projecting section for projecting range finding light onto an object; a light receiving section for receiving reflection signal light from the object; an integrating circuit for integrating an output from the light receiving section; a steady light component removing section for preventing a signal based on light irradiated steadily onto the light receiving section from being input to the integrating circuit; a determining section for determining a spot configuration of the reflection signal light or a contrast of an image incident onto the light receiving section according to the result of a first range finding step in which a preliminary range finding operation is performed accompanying the control of the light projecting section, without the steady light component removing section being operated; and a control section for determining, based on determination results by the determining section, whether to perform a second range finding step subsequent to the first range finding step or to perform a steady light component removing operation in the second range finding step.
Further, the fifth aspect of the present invention is a range finder device comprising: a light projecting section for projecting range finding light onto an object; a light receiving section for receiving reflection signal light from the object; an integrating circuit for integrating an output from the light receiving section; a steady light component removing section for preventing a signal based on light irradiated steadily onto the light receiving section from being input to the integrating circuit; a determining section for determining a spot configuration of the reflection signal light or a contrast of an image incident onto the light receiving section according to the result of a first range finding step in which a preliminary range finding operation is performed accompanying the control of the light projecting section, with the steady light component removing section being operated; and a control section for determining, based on determination results by the determining section, whether or not to perform a second range finding step subsequent to the first range finding step.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.